This invention relates to a composition and method for effecting superficial chemical skin peels, particularly, utilizing compositions containing salicylic acid.
Skin peeling techniques have long been used for therapeutic benefit to treat a wide spectrum of skin disorders deemed as being aesthetically or medically undesirable. Such skin disorders most commonly affect facial skin and include photodamaged skin, typically resulting from exposure to sunlight or other ultraviolet sources; hyperpigmentation, including melasma, mottled spots, “liver” or “age” spots, freckles; wrinkled, rough or “weathered” skin; and premalignant neoplasms (also called premalignant skin cancer) such as actinic keratoses.
Conventional skin peeling procedures include mechanical removal, e.g., dermabrasion or CO2 laser, and chemical-induced skin removal. Chemical skin peeling techniques are currently very popular for treating the skin disorders described above and are often categorized by the degree or amount of skin removal effected.
Chemical peels may be categorized as superficial, medium and deep chemical peels, depending on the depth of chemical wounding of the skin that occurs. Superficial chemical peels are those which remove or effect accelerated replacement or replenishment of the epidermis. Popular superficial chemical peeling agents include α-hydroxy acids, e.g., glycolic acid or other “fruit acids” such as citric and lactic acids; trichloroacetic acid; resorcinol and Jessner's solution. Medium depth peels penetrate to the papillary dermis and typically use 40-50% trichloroacetic acid as the chemical peeling agent. Deep peels penetrate to the reticular dermis and typically use phenol as the chemical peeling agent. Superficial chemical peels are most commonly used in treating skin disorders such as described above, particularly photodamaged skin, and glycolic acid is the most popular chemical peeling agent for such peels.
Jessner's solution, mentioned above, has been used in superficial chemical skin peeling to treat photodamaged skin and other facial skin disorders. Salicylic acid is one component utilized in Jessner's solution, an ethanol solution containing equal parts (about 14%) of resorcinol, salicylic acid and lactic acid (85%); see Brody, Chemical Peeling, Mosby Year Book, St. Louis, Mo., pp. 59-60 (1992) and Rubin, Manual of Chemical Peels, J. B. Lippincott Company, Philadelphia, Penn., pp. 79-88 (1995).
Salicylic acid is a well-known compound that is recognized for its usefulness as a “keratolytic” agent and as a precursor in the manufacture of salicylate derivatives, such as analgesics. Salicylic acid is a powder that is relatively insoluble in water and has been used at low concentrations in alcoholic solutions or in other carriers or, in solid form, as a plaster, paste or ointment composition.
U.S. Pat. No. 5,449,519 of Wolfe et al. describes cosmetic compositions with keratolytic and anti-acne activity, that contain a keratolytic compound, ie., salicylic acid, resorcinol and/or benzoyl peroxide, complexed to an amino- or hydroxy-containing carrier such as a protein. The compositions contain 0.1-30% keratolytic compound complex and 70-99.9% diluent, such as a cream, lotion, toner, or other cosmetically acceptable diluent.
Salicylic acid, benzoyl peroxide and resorcinol have long been utilized for acne treatment in aqueous ethanol solutions at low concentrations, e.g., less than about 10% salicylic acid (typically 1-7% salicylic acid) and less than about 20% benzoyl peroxide (typically 3-10% benzoyl peroxide). U.S. Pat. No 4,318,907 of Kligman et al. discloses such compositions but cautions against using higher concentrations of salicylic acid, noting (column 2, lines 49-52) that 10% salicylic acid with 5% benzoyl peroxide caused excessive redness and peeling in many patients treated.
Salicylic acid has been used in solid form for the treatment of warts, as a plaster containing 40% salicylic acid that is applied with adhesive tape to the wart for several days. Salicylic acid has also been utilized in chemical peels for treatment of photodamaged skin on the hands and forearms, in the form of a salicylic acid paste or ointment. Such treatments typically involve application of a thick coating of ointment, containing 50% salicylic acid, to the affected skin, then wrapping the treated areas with Saran Wrap® plastic wrap secured with tape, followed by a 48 hours occlusion period after which the dressing is removed; see Swinehart, “Salicylic Ointment Peeling of the Hands and Forearms”,J. Dermatol Surg. Oncol. 18, pp. 495-498 (1992). The inconvenience of this treatment is unacceptable for many patients, and Swinehart does not suggest that this technique might be usefull for treatment of facial skin. Besides the inconvenience to the patient during treatment, this procedure is also subject to a risk of salicylism, i.e., toxic effects from systemic absorption of salicylic acid during the prolonged treatment period. The use of a salicylic acid paste or ointment as described by Swinehart, supra, for treating damaged skin on the hands and forearms is also mentioned by Brody, op. cit., at pages 60-63 and by Rubin, op. cit., at pages 103-109.
U.S. Pat. No. 4,954,487 of Cooper et al. describes topically administered pharmaceutical compositions with a two-component skin penetration enhancer for delivering a pharmaceutical active across intact skin. The compositions may contain antibiotics, local anesthetics, benzoyl peroxide or non-steroidal anti-inflammatory drugs (NSAIDs), including salicylic acid, at a concentration of 0.01-35 wt % in 0-70% ethanol with 5-99% skin penetration enhancer. The antibiotic containing or benzoyl peroxide-containing compositions are described as useful for the treatment of acne, but the NSAID-containing compositions are described only as useful for treating and preventing pain and inflammation in humans and lower animals.
A need exists for a superficial chemical skin peeling technique that provides exceptional improvement for skin disorders such as described earlier, without the adverse side effects or drawbacks of conventional superficial chemical peels.